A technique was developed to measure the thermal expansion of solids in the temperature range from −50 to 175°C. The technique uses strain gages to measure expansion and Type J (iron/constantan) thermocouples to measure temperature. Measurements were made on pure platinum and on copper and tungsten standard reference materials obtained from the National Bureau of Standards. Results were compared with the certified values of expansion. The maximum difference between measurements made in this study and the certified values was 0.26 × 10−6/°C for the mean coefficients and 0.40 × 10−6/°C for the instantaneous coefficients. The standard deviation of the measurements of the mean coefficients was 0.11 × 10−6/°C.